This invention relates to the art of increasing the filling power of tobacco lamina filler. More particularly, this invention relates to a process whereby the filling power of tobacco lamina filler having a low initial moisture content and which may have been previously treated to increase its filling power, is increased without the use of exogenous puffing or blowing agents.
During curing, the moisture content of tobacco leaves is greatly reduced resulting in shrinkage of the leaf structure and a decrease in filling power. Additionally, the shredding or cutting techniques generally employed to convert the cured tobacco leaves into filler may result in some lamination and compression of the tobacco, thereby decreasing the filling power even further. Many processes have been devised for increasing the filling power of cured tobacco for reasons well known in the art.
The heretofore known processes may be broadly characterized as involving penetration or impregnation of the tobacco with impregnants (blowing or puffing agents) which when removed during a subsequent expansion process step generate elevated pressure in and expand the tobacco.
Among the impregnants which have been employed are pressurized steam, air, water, organic solvents, ammonia, carbon dioxide, combinations of ammonia and carbon dioxide, and compounds capable of liberating a gas when subjected to chemical decomposition, as by heating. Among the means disclosed for removing the impregnant to expand the cell walls are a sudden reduction in pressure, freeze-drying, convection heating, radiant transfer (infrared), and the application of a microwave field.
While a number of the known processes may be employed to provide a satisfactory expanded tobacco product, which may then be blended with an unexpanded tobacco and formed into cigarettes or the like, the known processes do possess certain disadvantages. The use of certain impregnants, such as halogenated hydrocarbons which are foreign to tobacco, may not be completely satisfactory because some of the materials employed are not always desired as additives and the introduction, in considerable concentration, of such foreign materials presents the problem of removing the expansion agent after the treatment has been completed in order to avoid affecting aroma and other properties of the smoke. Moreover, aside from the aforementioned disadvantages, the use of such foreign materials adds to the overall cost of producing tobacco end products.
The earlier reported processes employing water as the impregnant tend to produce a more satisfactory result with tobacco stems than with tobacco lamina filler. One belief was that the lamina cellular structure was difficult to impregnate and that therefore most of the water remained on the surface. This belief may have motivated some of those skilled in the art to try vacuum impregnation and longer bulking times. More recent processes employing water as the impregnant have been successful in substantially increasing the filling power of tobacco lamina filler when water was used as the sole impregnant in an amount, measured as oven volatiles, within the range of from 20% 80% for one process, preferably 30% to about 80%, and 8% to about 30% for a second process, preferably 10% to 14%. These processes teach away from the use of OV values below their respective broader ranges.